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John C. Baez @johncarlosbaez.bsky.social · 8m

Grothendieck talked about how the sea of results slowly rises, almost imperceptibly. This book cover makes it look pretty threatening. Which is how students perceive Grothendieck's work. 😆

John C. Baez @johncarlosbaez.bsky.social · 11m

So someone thinks science isn't creative work? I'm confused.

John C. Baez @johncarlosbaez.bsky.social · 12h

I don't understand it, but this article claims to explain it.

"This article outlines the use of the Brunauer-Emmett-Teller (BET) method and Barrett-Joyner-Halenda (BJH) method for the calculation of surface area and pore volume, respectively...."

app.jove.com/t/65716/dete...

Determining Surface Areas and Pore Volumes of Metal-Organic Frameworks

Georgia Institute of Technology. This article describes the use of nitrogen porosimetry to characterize metal-organic frameworks, using UiO-66 as a representative material.

app.jove.com

John C. Baez @johncarlosbaez.bsky.social · 12h

In principle yes, but it seems they haven't reached the goals people want for them.

chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/...

Metal‐Organic Frameworks (MOFs) As Hydrogen Storage Materials At Near‐Ambient Temperature

Hydrogen as is difficult to store in significant quantities via physical methods especially at near-ambient temperatures (248–373 K). Metal-organic frameworks (MOFs) have the potential to increase hy...

chemistry-europe.onlinelibrary.wiley.com

John C. Baez @johncarlosbaez.bsky.social · 19h

So I wrote a few blog articles. But I decided, unsurprisingly, that they wouldn't scale up enough to do any good for climate change. So I quit, and never got paid for the articles I wrote.

Still, they are a cool technology and have lots of potential uses.

Synthesis of the MIL-101 metal-organic framework. Each green octahedron consists of one Cr atom in the center and six oxygen atoms (red balls) at the corners.

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John C. Baez @johncarlosbaez.bsky.social · 19h

In 2019, someone offered to pay me to publicize their business involving metal-organic frameworks. The idea proposed to me was that these could be used to soak up greenhouse gases, and that I should blog about this.

johncarlosbaez.wordpress.com/2019/03/11/m...

Metal-Organic Frameworks

I’ve been talking about new technologies for fighting climate change, with an emphasis on negative carbon emissions. Now let’s begin looking at one technology in more detail. This will …

johncarlosbaez.wordpress.com

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John C. Baez @johncarlosbaez.bsky.social · 19h

Gas molecules like to sit inside these holes. So, perhaps surprisingly at first, you can pack a lot more gas in a cylinder containing a metal organic framework than you can in an empty cylinder at the same pressure!

A large yellow sphere representing a hole where gas molecules can go, surrounded by blue tetaherad and struts connecting small red and blue dots.

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John C. Baez @johncarlosbaez.bsky.social · 19h

Susumu Kitagawa, Richard Robson and Omar M. Yaghi won the Nobel prize in chemistry for metal-organic-frameworks!

These are molecular structures built from metal atoms and organic compounds, full of microscopic holes. One gram can have a surface area of more than 12,000 square meters!

Yellow and orange balls between a complex lattice-work of blue tetrahedra.

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John C. Baez @johncarlosbaez.bsky.social · 19h

If you look at my book, which seems like a big project, start by looking at just the pictures.

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John C. Baez @johncarlosbaez.bsky.social · 19h

You don't really need to know physics to understand some of the key tensors in general relativity, like the metric tensor and Riemann tensor. Those are about geometry, and Einstein needed his old college pal Marcel Grossman to explain them to him. But other tensors are about physics.

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John C. Baez @johncarlosbaez.bsky.social · 20h

"How do you visualize something wild like a rank (5, 5) (contravariant, covariant) tensor?"

Have you ever needed to do that in a physics course? In my physics courses the worst thing I've met is the Riemann tensor, which is rank (1, 3). And that's perfectly visualizable.

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John C. Baez @johncarlosbaez.bsky.social · 21h

Yes, Penrose introduced a lot of these ideas:

math.ucr.edu/home/baez/pe...

Penrose on Spin Networks

math.ucr.edu

John C. Baez @johncarlosbaez.bsky.social · 21h

"Maybe it's a good thing to learn how to model physical processes/phenomena without being able to "get a picture of" the thing."

I think most physicists rely heavily on getting a picture of the thing. What they do is increase their visualization powers.

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John C. Baez @johncarlosbaez.bsky.social · 1d

It's a fascinating process, getting from the math to the physical intuition.

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John C. Baez @johncarlosbaez.bsky.social · 1d

In reality this is what we do: compare clocks and rulers to each other and throw out the ones that disagree too much. It's a fascinating process, especially in this regard: how in the world do we create "more accurate" clocks and rulers and know they are more accurate?

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John C. Baez @johncarlosbaez.bsky.social · 1d

The good things is that I'm working on that now so it's on my mind.

Varadarajan wrote a good book "The Geometry of Quantum Mechanics", but I'd take a much more light-weight approach.

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John C. Baez @johncarlosbaez.bsky.social · 1d

I would never talk about string theory. Someday I might do QFT for mathematicians. But for now I'm choosing from the list of topics I listed, because those are the topics where I already have notes written up.

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John C. Baez @johncarlosbaez.bsky.social · 1d

You have to choose from the list, because I won't make a series of videos on a topic where I don't already have notes prepared! At least not at first.

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John C. Baez @johncarlosbaez.bsky.social · 1d

That's the one I'll probably do first!

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John C. Baez @johncarlosbaez.bsky.social · 1d

Today I learned you're not safe from winning the Nobel, even if you go to an undisclosed location in Idaho.

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John C. Baez @johncarlosbaez.bsky.social · 1d

If I made a series of videos about something, what would you like?

The Standard Model? Grand unified theories? Clifford algebras? The octonions? Entropy? Category theory? Quantum logic and projective geometry? Visually beautiful math?

A hyperbolic honeycomb called {6,3,5}, since it’s built from flat planes tiled by regular hexagons, 3 meeting at each vertex, and 5 of these planes meeting along each edge of the honeycomb. White struts with a blue background.

Drawn by Roice Nelson: https://blogs.ams.org/visualinsight/2014/04/15/635-honeycomb/

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John C. Baez @johncarlosbaez.bsky.social · 1d

Re your kvetch: I find Mastodon too quiet but I *always* get some fascinating responses to my science posts, no matter how technical they are. For example this:

mathstodon.xyz/@pschwahn/11...

I find Bluesky disappointing - mostly just politics, which is understandable, but still.... (2/2)

Paul Schwahn (@[email protected])

Content warning: Octonions and the Standard Model

mathstodon.xyz

John C. Baez @johncarlosbaez.bsky.social · 1d

Thanks! I hope that problem set turns up. This paper is pretty good at explaining just the amount of string diagrams needed for an intro to vector calculus course, but (of course) I would do some things differently - and I bet you would too. (1/2)

arxiv.org/abs/1911.00892

Boosting Vector Calculus with the Graphical Notation

Learning vector calculus techniques is one of the major missions to be accomplished by physics undergraduates. However, beginners report various difficulties dealing with the index notation due to its...

arxiv.org

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John C. Baez @johncarlosbaez.bsky.social · 1d

Грег Иган looks like the name of an alien supervillain.

Greg Egan @gregegansf.bsky.social · 2d

Just received author’s copies of this translation of “The Clockwork Rocket” [Book One of the Orthogonal Trilogy] from Explorer Books, a Russian-language publisher in the Netherlands.

Explorer Books: explorerbooks.org/product/cloc...

About the Orthogonal Trilogy:
www.gregegan.net/ORTHOGONAL/O...

Photo of front cover and spine of Russian translation of “The Clockwork Rocket”, showing a rocket engine firing against a backdrop of colour-trails of stars.

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John C. Baez @johncarlosbaez.bsky.social · 1d

Imagining yourself as part of an ensemble is always tricky. I guess you know about "quantum immortality", the view that the many-worlds interpretation will make each of us wind up in a branch where we are improbably old ('cause otherwise we wouldn't be there).

I don't buy it, but I'm only 64.

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